Hyperconjugation

This is the process by which a carbocation is stabilised by an alkyl group. It is defined as:

The stabilising interaction that results from the interaction of the electrons in a σ-bond (usually C-H or C-C) with an adjacent empty or partially filled p-orbital or a π-orbital to give an extended molecular orbital that increases the stability of the system.

This is different from the inductive effect, where the electron pull is derived from the electronegativity of electrons and not from overlapping of orbitals.